U.S. patent number 8,862,397 [Application Number 13/859,233] was granted by the patent office on 2014-10-14 for article transport facility.
This patent grant is currently assigned to Daifuku Co., Ltd.. The grantee listed for this patent is Daifuku Co., Ltd.. Invention is credited to Yoshimasa Hara, Koji Kubota, Toshisada Mariyama, Natsuo Takagawa, Masanori Tsujimoto.
United States Patent |
8,862,397 |
Tsujimoto , et al. |
October 14, 2014 |
Article transport facility
Abstract
Disclosed is an article transport facility in which interference
between an article transport vehicle and an interfering object is
prevented. A position detector is provided on the ground side for
detecting the position of an interfering object, and an external
managing device issues a deceleration command to the article
transport vehicle if the distance from the article transport
vehicle to the interfering object becomes less than or equal to a
predetermined low speed distance, based on position information for
the interfering object and travel position information for the
article transport vehicle. A vehicle side travel controller changes
a target travel speed from a normal travel speed to a reduced
travel speed which is lower, or less, than the normal travel speed
while the target travel speed is set to the normal travel speed, if
the deceleration command is issued from the external managing
device.
Inventors: |
Tsujimoto; Masanori (Tokyo,
JP), Hara; Yoshimasa (Tokyo, JP), Takagawa;
Natsuo (Gamo-gun, JP), Mariyama; Toshisada
(Gamo-gun, JP), Kubota; Koji (Gamo-gun,
JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Daifuku Co., Ltd. |
Osaka |
N/A |
JP |
|
|
Assignee: |
Daifuku Co., Ltd. (Osaka,
JP)
|
Family
ID: |
49325840 |
Appl.
No.: |
13/859,233 |
Filed: |
April 9, 2013 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20130275045 A1 |
Oct 17, 2013 |
|
Foreign Application Priority Data
|
|
|
|
|
Apr 11, 2012 [JP] |
|
|
2012-090590 |
Mar 8, 2013 [JP] |
|
|
2013-047060 |
|
Current U.S.
Class: |
701/517 |
Current CPC
Class: |
G05D
1/0223 (20130101); B60P 1/00 (20130101); G05D
1/0297 (20130101); G05D 1/0261 (20130101); G08G
1/164 (20130101); G05D 2201/0216 (20130101) |
Current International
Class: |
G08G
1/16 (20060101) |
Field of
Search: |
;701/23-27,300,301,408-411,517 ;104/26.2,295,300 ;198/322,323 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Trammell; James
Assistant Examiner: Butler; Rodney
Attorney, Agent or Firm: The Webb Law Firm
Claims
What is claimed is:
1. An article transport facility comprising: an article transport
vehicle configured to travel by an operation of a travel actuating
device and along a travel path extending by way of a plurality of
article transfer locations; a ground side travel controller which
issues a travel command to the article transport vehicle; a vehicle
side travel controller which is provided to the article transport
vehicle, and which controls operation of the travel actuating
device based on detected information from a travel position
detector which detects a travel position of the article transport
vehicle, wherein the vehicle side travel controller is configured
to control operation of the travel actuating device based on travel
position information detected by the travel position detector and
travel command information from the ground side travel controller
in order to cause the article transport vehicle to travel along the
travel path toward a target travel position at a target travel
speed; a position detector provided on a ground side for detecting
a position of an interfering object that exists in a detection
target area which includes an area in which the travel path is
installed; and an external managing device which issues a
deceleration command to the article transport vehicle if and when
the position of the interfering object with respect to the article
transport vehicle is in a low speed area, which is determined in
advance with respect to the position of the article transport
vehicle, based on position information of the interfering object
from the position detector and travel position information of the
article transport vehicle; wherein: the vehicle side travel
controller is configured to change the target travel speed from a
normal travel speed to a reduced travel speed which is less than
the normal travel speed if and when the deceleration command is
issued from the external managing device while the target travel
speed is set to the normal travel speed, the position detector is a
wireless position measuring device which includes wireless tags
configured to output positioning wireless signals which are
wireless signals for position measurement, a plurality of receivers
configured to receive the positioning wireless signals from the
wireless tags that exist in the detection target area, and a
position calculation portion which calculates positions of the
wireless tags in the detection target area based on received
information from the plurality of receivers wherein the wireless
position measuring device performs a position measurement process
in which the position of the interfering object in the detection
target area is calculated, a plurality of the wireless tags are
provided to each of the interfering objects, each of the receivers
is configured to receive the positioning wireless signals from only
one of the wireless tags at one time, and to receive the
positioning wireless signals from the plurality of wireless tags
such that the receptions of the positioning wireless signals are
staggered over time, the wireless position measuring device is
configured to measure the positions of the interfering objects at
every processing time by repeatedly performing the position
measurement process at every processing time, and to perform, as
the position measurement process, both of a multiple tag position
measurement process in which the position of each of the
interfering objects is calculated based on a position of each of
the plurality of wireless tags associated with each of the
interfering objects, and a single tag position measurement process
in which the position of each of the interfering objects is
calculated to be a position of one of the plurality of wireless
tags that are associated with the each of the interfering objects,
the external managing device is configured to set the deceleration
command such that the shorter a distance between the article
transport vehicle and the interfering object is, the lower a speed
indicated by the deceleration command is, and if the deceleration
command set for a distance, between the article transport vehicle
and the interfering object, calculated based on the position of the
interfering object calculated in the multiple tag position
measurement process is different from the deceleration command set
for a distance, between the article transport vehicle and the
interfering object, calculated based on the position of the
interfering object calculated in the single tag position
measurement process, then the external managing device is
configured to select and issue the deceleration command that
indicates a slower speed.
2. The article transport facility as defined in claim 1, wherein
the low speed area is defined to be a fan-shaped area whose radius
is equal to a low speed distance defined in advance and which has a
center at the position of the article transport vehicle and spreads
forwardly of the article transport vehicle in plan view, and
wherein the external managing device is configured to transmit the
deceleration command to the article transport vehicle if and when a
distance from the article transport vehicle to the interfering
object becomes less than or equal to the low speed distance.
3. The article transport facility as defined in claim 1, wherein
provided as the position detector are a large area detector for
detecting the position of the interfering object in an entire area
of the detection target area, and a small area detector for
detecting the position of the interfering object in an area in the
detection target area in which detecting the position of an
interfering object with the large area detector is difficult.
4. The article transport facility as defined in claim 1, wherein
the vehicle side travel controller is configured to change the
normal travel speed to a lower speed based on a travel condition,
and to maintain the target travel speed at the normal travel speed
even if the deceleration command is issued from the ground side
travel controller while the target travel speed is set to the
normal travel speed if the normal travel speed is less than the
reduced travel speed.
5. The article transport facility as defined in claim 1, wherein
the external managing device is configured to be able to determine
a kind of interfering object based on detected information from the
position detector, and to set a predefined low speed distance
differently depending on the kind of interfering object.
6. The article transport facility according to claim 1, wherein:
the article transport vehicle includes a presence detector for
detecting a presence of the interfering object located forwardly in
the travel direction of the article transport vehicle, the vehicle
side travel controller is configured to change the travel speed of
the article transport vehicle from the normal travel speed to a
reduced travel speed which is less than the normal travel speed if
and when an interfering object is detected by the presence detector
while the target travel speed is set to the normal travel speed,
and the position detector is configured to detect an interfering
object at a position where it is difficult to detect the
interfering object with the presence detector.
7. The article transport facility as defined in claim 1, wherein
the external managing device is configured to be able to set a low
speed distance defined in advance for when the interfering object
is located forwardly of the article transport vehicle in the travel
direction to be different from the low speed distance defined in
advance for when the interfering object is located rearwardly of
the article transport vehicle in the travel direction.
8. An article transport facility comprising: an article transport
vehicle configured to travel by an operation of a travel actuating
device and along a travel path extending by way of a plurality of
article transfer locations; a ground side travel controller which
issues a travel command to the article transport vehicle; a vehicle
side travel controller which is provided to the article transport
vehicle, and which controls operation of the travel actuating
device based on detected information from a travel position
detector which detects a travel position of the article transport
vehicle, wherein the vehicle side travel controller is configured
to control operation of the travel actuating device based on travel
position information detected by the travel position detector and
travel command information from the ground side travel controller
in order to cause the article transport vehicle to travel along the
travel path toward a target travel position at a target travel
speed; a position detector provided on a ground side for detecting
a position of an interfering object that exists in a detection
target area which includes an area in which the travel path is
installed; and an external managing device which issues a
deceleration command to the article transport vehicle if and when
the position of the interfering object with respect to the article
transport vehicle is in a low speed area, which is determined in
advance with respect to the position of the article transport
vehicle, based on position information of the interfering object
from the position detector and travel position information of the
article transport vehicle; wherein: the vehicle side travel
controller is configured to change the target travel speed from a
normal travel speed to a reduced travel speed which is less than
the normal travel speed if and when the deceleration command is
issued from the external managing device while the target travel
speed is set to the normal travel speed, the position detector is a
wireless position measuring device which includes wireless tags
that are provided to the interfering object and that are configured
to output positioning wireless signals which are wireless signals
for position measurement, a plurality of receivers configured to
receive the positioning wireless signals from the wireless tags
that exist in the detection target area, and a position calculation
portion which calculates positions of the wireless tags in the
detection target area based on received information from the
plurality of receivers wherein the wireless position measuring
device performs a position measurement process in which the
position of the interfering object in the detection target area is
calculated, a plurality of the wireless tags are provided to each
of the interfering objects, the receiver is configured to receive
the positioning wireless signal from only one of the wireless tags
at one time and to receive the positioning wireless signals from
the plurality of wireless tags such that the receptions of the
positioning wireless signals are staggered over time, the wireless
position measuring device is configured to measure the positions of
the interfering objects at every processing time by repeatedly
performing the position measurement process at every processing
time, and to perform, as the position measurement process, both of
a multiple tag position measurement process in which the position
of each of the interfering objects is calculated based on a
position of each of the plurality of wireless tags associated with
each of the interfering objects, and a single tag position
measurement process in which the position of each of the
interfering objects is calculated to be a position of one of the
plurality of wireless tags that are associated with the each of the
interfering objects, and the external managing device is configured
to issue the deceleration command if and when at least one of: a
distance, between the article transport vehicle and the interfering
object, calculated based on the position of the interfering object
calculated in the multiple tag position measurement process; and a
distance, between the article transport vehicle and the interfering
object, calculated based on the position of the interfering object
calculated in the single tag position measurement process, becomes
less than or equal to a distance from the article transport vehicle
to an outer edge of the low speed area.
9. The article transport facility as defined in claim 8, wherein
the low speed area is defined to be a fan-shaped area whose radius
is equal to a low speed distance defined in advance and which has a
center at the position of the article transport vehicle and spreads
forwardly of the article transport vehicle in plan view, and
wherein the external managing device is configured to transmit the
deceleration command to the article transport vehicle if and when a
distance from the article transport vehicle to the interfering
object becomes less than or equal to the low speed distance.
10. The article transport facility as defined in claim 8, wherein
provided as the position detector are a large area detector for
detecting the position of the interfering object in an entire area
of the detection target area, and a small area detector for
detecting the position of the interfering object in an area in the
detection target area in which detecting the position of an
interfering object with the large area detector is difficult.
11. The article transport facility as defined in claim 8, wherein
the vehicle side travel controller is configured to change the
normal travel speed to a lower speed based on a travel condition,
and to maintain the target travel speed at the normal travel speed
even if the deceleration command is issued from the ground side
travel controller while the target travel speed is set to the
normal travel speed if the normal travel speed is less than the
reduced travel speed.
12. The article transport facility as defined in claim 8, wherein
the external managing device is configured to be able to determine
a kind of interfering object based on detected information from the
position detector, and to set a predefined low speed distance
differently depending on the kind of interfering object.
13. The article transport facility according to claim 8, wherein:
the article transport vehicle includes a presence detector for
detecting a presence of the interfering object located forwardly in
the travel direction of the article transport vehicle, the vehicle
side travel controller is configured to change the travel speed of
the article transport vehicle from the normal travel speed to a
reduced travel speed which is less than the normal travel speed if
and when an interfering object is detected by the presence detector
while the target travel speed is set to the normal travel speed,
and the position detector is configured to detect an interfering
object at a position where it is difficult to detect the
interfering object with the presence detector.
14. The article transport facility as defined in claim 8, wherein
the external managing device is configured to be able to set a low
speed distance defined in advance for when the interfering object
is located forwardly of the article transport vehicle in the travel
direction to be different from the low speed distance defined in
advance for when the interfering object is located rearwardly of
the article transport vehicle in the travel direction.
15. An article transport facility comprising: an article transport
vehicle configured to travel by an operation of a travel actuating
device and along a travel path extending by way of a plurality of
article transfer locations; a ground side travel controller which
issues a travel command to the article transport vehicle; a vehicle
side travel controller which is provided to the article transport
vehicle, and which controls operation of the travel actuating
device based on detected information from a travel position
detector which detects a travel position of the article transport
vehicle, wherein the vehicle side travel controller is configured
to control operation of the travel actuating device based on travel
position information detected by the travel position detector and
travel command information from the ground side travel controller
in order to cause the article transport vehicle to travel along the
travel path toward a target travel position at a target travel
speed; a position detector provided on a ground side for detecting
a position of an interfering object that exists in a detection
target area which includes an area in which the travel path is
installed; and an external managing device which issues a
deceleration command to the article transport vehicle if and when
the position of the interfering object with respect to the article
transport vehicle is in a low speed area, which is determined in
advance with respect to the position of the article transport
vehicle, based on position information of the interfering object
from the position detector and travel position information of the
article transport vehicle; wherein: the vehicle side travel
controller is configured to change the target travel speed from a
normal travel speed to a reduced travel speed which is less than
the normal travel speed if and when the deceleration command is
issued from the external managing device while the target travel
speed is set to the normal travel speed, the article transport
vehicle includes a presence detector for detecting a presence of
the interfering object located forwardly in the travel direction of
the article transport vehicle, and an auxiliary travel controller
which controls operation of the travel actuating device based on
the detected information from the presence detector, and the
auxiliary travel controller is configured to change the travel
speed of the article transport vehicle from the normal travel speed
to a reduced travel speed which is less than the normal travel
speed if and when the interfering object is detected by the
presence detector while the target travel speed is set to the
normal travel speed.
16. The article transport facility as defined in claim 15, wherein
the low speed area is defined to be a fan-shaped area whose radius
is equal to a low speed distance defined in advance and which has a
center at the position of the article transport vehicle and spreads
forwardly of the article transport vehicle in plan view, and
wherein the external managing device is configured to transmit the
deceleration command to the article transport vehicle if and when a
distance from the article transport vehicle to the interfering
object becomes less than or equal to the low speed distance.
17. The article transport facility as defined in claim 15, wherein
provided as the position detector are a large area detector for
detecting the position of the interfering object in an entire area
of the detection target area, and a small area detector for
detecting the position of the interfering object in an area in the
detection target area in which detecting the position of an
interfering object with the large area detector is difficult.
18. The article transport facility as defined in claim 15, wherein
the vehicle side travel controller is configured to change the
normal travel speed to a lower speed based on a travel condition,
and to maintain the target travel speed at the normal travel speed
even if the deceleration command is issued from the ground side
travel controller while the target travel speed is set to the
normal travel speed if the normal travel speed is less than the
reduced travel speed.
19. The article transport facility as defined in claim 15, wherein
the position detector is configured to transmit interfering object
presence information to the presence detector if and when the
distance from the article transport vehicle to the interfering
object becomes less than or equal to a deceleration distance
defined in advance, based on position information of the detected
interfering object and travel position information for the article
transport vehicle, and wherein the presence detector is configured
to be changed to a detection state in which a presence of the
interfering object is detected, upon receiving the interfering
object presence information from the said position detector.
20. The article transport facility as defined in claim 15, wherein
the external managing device is configured to be able to determine
a kind of interfering object based on detected information from the
position detector, and to set a predefined low speed distance
differently depending on the kind of interfering object.
21. The article transport facility according to claim 15, wherein:
the article transport vehicle includes a presence detector for
detecting a presence of the interfering object located forwardly in
the travel direction of the article transport vehicle, the vehicle
side travel controller is configured to change the travel speed of
the article transport vehicle from the normal travel speed to a
reduced travel speed which is less than the normal travel speed if
and when an interfering object is detected by the presence detector
while the target travel speed is set to the normal travel speed,
and the position detector is configured to detect an interfering
object at a position where it is difficult to detect the
interfering object with the presence detector.
22. The article transport facility as defined in claim 15, wherein
the external managing device is configured to be able to set a low
speed distance defined in advance for when the interfering object
is located forwardly of the article transport vehicle in the travel
direction to be different from the low speed distance defined in
advance for when the interfering object is located rearwardly of
the article transport vehicle in the travel direction.
Description
FIELD OF THE INVENTION
The present invention relates to an article transport facility
comprising an article transport vehicle configured to travel by an
operation of a travel actuating device and along a travel path
extending by way of a plurality of article transfer locations; a
ground side travel controller which issues a travel command to the
article transport vehicle wherein the article transport vehicle has
a vehicle side travel controller which controls operation of the
travel actuating device based on detected information from a travel
position detector which detects a travel position of the article
transport vehicle, wherein the vehicle side travel controller is
configured to control operation of the travel actuating device
based on travel position information detected by the travel
position detector and travel command information from the ground
side travel controller in order to cause the article transport
vehicle to travel along the travel path toward a target travel
position at a target travel speed.
BACKGROUND
Facilities such as the article transport facility described above
are configured to cause article transport vehicles to travel based
on travel commands from a ground side travel controller to
transport articles among article transfer locations with the
article transport vehicles.
And an example of such article transport facility is disclosed in
JP Publication of Application No. 2006-259877 (Patent Document
1).
In Patent Document 1, an obstacle sensor for detecting the position
of an article is provided to each article transport vehicle.
And a vehicle side travel controller is configured to change the
target travel speed to a reduced travel speed which is less than
the normal travel speed when an article exists within a set
distance from the article transport vehicle, based on detected
information for the obstacle sensor.
Incidentally, in the conventional article transport facility
described above, articles may be placed directly on the floor at a
side of the travel path.
The positions of such articles are stored in advance in the vehicle
side travel controller so that they would not be determined to be
interfering objects or obstacles.
However, in the article transport facility disclosed in the Patent
Document 1 described above, the obstacle sensor provided to the
article transport vehicle detects the position of any interfering
objects.
Thus, for example, if there is an article, such as an article that
is directly placed on the floor, between an article transport
vehicle and an interfering object, and if that article is not a
target of detection and thus is not determined to be an interfering
object, then because the interfering object can be hidden by this
article that is not a target of detection, the obstacle sensor
would not be able to detect the interfering object.
And if the interfering object is a movable object such as a human
worker, etc., the interfering object may move and appear suddenly
in front of the article transport vehicle.
And when this happens, the interfering object can be detected by
the obstacle sensor only after the interfering object appears in
front of the article a transport vehicle.
Thus, the article transport vehicle would be traveling at a normal
travel speed when the interfering object sensor detects an
interfering object; thus, there is a possibility that the article
transport vehicle may interfere, or collide, with the interfering
object before the vehicle is able to slow down and stop.
SUMMARY OF THE INVENTION
In light of the state of art described above, an article transport
facility is desired that can properly detect interfering objects
and that makes it easier to avoid interference between article
transport vehicles and interfering objects.
An article transport facility in accordance with the present
invention comprises:
an article transport vehicle configured to travel by an operation
of a travel actuating device and along a travel path extending by
way of a plurality of article transfer locations;
a ground side travel controller which issues a travel command to
the article transport vehicle;
a vehicle side travel controller which is provided to the article
transport vehicle, and which controls operation of the travel
actuating device based on detected information from a travel
position detector which detects a travel position of the article
transport vehicle,
wherein the vehicle side travel controller is configured to control
operation of the travel actuating device based on travel position
information detected by the travel position detector and travel
command information from the ground side travel controller in order
to cause the article transport vehicle to travel along the travel
path toward a target travel position at a target travel speed;
a position detector provided on a ground side for detecting a
position of an interfering object that exists in a detection target
area which includes an area in which the travel path is installed;
and an external managing device which issues a deceleration command
to the article transport vehicle if and when the position of the
interfering object with respect to the article transport vehicle is
in a low speed area, which is defined in advance with respect to
the position of the article transport vehicle, based on position
information of the interfering object from the position detector
and travel position information of the article transport
vehicle;
wherein the vehicle side travel controller is configured to change
the target travel speed from the normal travel speed to a reduced
travel speed which is less than the normal travel speed if and when
the deceleration command is issued from the external managing
device while the target travel speed is set to the normal travel
speed.
With the above-described arrangement, since the position detector
is located on the ground side and not on the article transport
vehicle, the position detector can be provided so as to be able to
detect an interfering object that is located at a position which is
hard to detect from the article transport vehicle, and with fewer
restrictions for the installing location.
Thus, an interfering object can be properly detected by the
position detector even if the object is located at a position which
is hard to detect from the article transport vehicle.
And the external managing device issues the deceleration command to
the article transport vehicle if and when the position of the
interfering object with respect to the article transport vehicle is
in the low speed area, which is defined in advance with respect to
the position of the article transport vehicle, based on position
information from the position detector.
When the deceleration command is issued, because the vehicle side
travel controller changes the target travel speed, at which the
article transport vehicle is caused to travel, from the normal
travel speed to the reduced travel speed, the travel speed of the
article transport vehicle is lowered.
Thus, even if an interfering object appears suddenly in front of
the article transport vehicle, the travel speed of the article
transport vehicle can be lowered to the reduced travel speed before
the interfering object appears suddenly.
Therefore, the facility makes it easier for the article transport
vehicle to avoid interfering with an interfering object.
For example, even if an interfering object appears suddenly in
front of the article transport vehicle, it is easier to for the
article transport vehicle to stop before the vehicle interferes
with the interfering object.
And when the interfering object is a human worker, it is easier for
the human worker to avoid interfering with the article transport
vehicle because the travel speed of the article transport vehicle
is low.
Examples of preferable embodiments of the present invention are
described next.
In an embodiment of the article transport facility in accordance
with the present invention, the low speed area is preferably
defined to be a fan-shaped area whose radius is equal to a low
speed distance defined in advance and which has its center at the
position of the article transport vehicle and spreads forwardly of
the article transport vehicle in plan view.
And the external managing device is preferably configured to
transmit the deceleration command to the article transport vehicle
if and when a distance from the article transport vehicle to the
interfering object becomes less than or equal to the low speed
distance.
With the above-described arrangement, because the low speed area is
a fan-shaped area whose radius is equal to the low speed distance
defined in advance, the external managing device is able to make a
determination as to whether the position of the interfering object
with respect to the article transport vehicle is in the low speed
area defined in advance, or predetermined, with respect to the
position of the article transport vehicle, using a simple method of
determining if the distance from the article transport vehicle to
the interfering object is less than or equal to the low speed
distance.
In an embodiment of the article transport facility in accordance
with the present invention, the position detector is preferably a
wireless position measuring device which preferably includes
wireless tags that are provided to the interfering object and that
are configured to output positioning wireless signals which are
wireless signals for position measurement, a plurality of receivers
configured to receive the positioning wireless signals from the
wireless tags that exist in the detection target area, and a
position calculation portion which calculates positions of the
wireless tags in the detection target area based on received
information from the plurality of receivers wherein the wireless
position measuring device performs a position measurement process
in which the position of the interfering object in the detection
target area is calculated, wherein a plurality of the wireless tags
are preferably provided to each of the interfering objects, wherein
the receiver is preferably configured to receive the positioning
wireless signal from only one of the wireless tags at one time and
to receive the positioning wireless signals from the plurality of
wireless tags such that the receptions of the positioning wireless
signals are staggered over time, wherein the wireless position
measuring device is preferably configured to measure the positions
of the interfering objects at every processing time by repeatedly
performing the position measurement process at every processing
time, and to perform, as the position measurement process, both of
a multiple tag position measurement process in which the position
of each of the interfering objects is calculated based on a
position of each of the plurality of wireless tags associated with
each of the interfering objects, and a single tag position
measurement process in which the position of each of the
interfering objects is calculated to be a position of one of the
plurality of wireless tags that are associated with the each of the
interfering objects, and wherein the external managing device is
preferably configured to set the deceleration command such that the
shorter a distance between the article transport vehicle and the
interfering object is, the lower a speed indicated by the
deceleration command is, and wherein, if the deceleration command
set for a distance, between the article transport vehicle and the
interfering object, calculated based on the position of the
interfering object calculated in the multiple tag position
measurement process is different from the deceleration command set
for a distance, between the article transport vehicle and the
interfering object, calculated based on the position of the
interfering object calculated in the single tag position
measurement process, the external managing device is preferably
configured to select and issue the deceleration command that
indicates a slower speed.
When the position of an interfering object is measured using
positioning wireless signals from a single tag, the calculation may
show a position that is different from the actual position of the
wireless tag as the position of the interfering object, depending
on the quality of the electromagnetic waves and on measurement
accuracy, among other factors.
For this reason, a plurality of the wireless tags are provided to
each of the interfering objects and the multiple tag position
measurement process is performed in which the position calculation
portion calculates the position of each of the plurality of the
wireless tags so that the position of the interfering object is
calculated based on the position of each of the plurality of
wireless tags.
This reduces the difference between the measured position and the
actual position to the extent possible so that the position of an
interfering object can be measured accurately. As the multiple tag
position measurement process, it is possible, for example, to take
an average of the positions of the plurality of wireless tags.
In addition, the wireless position measuring device repeatedly
performs the position measurement process at every processing time,
and updates and stores the positions of the wireless tags obtained
in the latest process.
Thus, the position of the interfering object obtained in the latest
process may always be kept track of based on the positions of the
wireless tags obtained in the latest process.
However, each receiver can receive the positioning wireless signal
from only one of the wireless tags at one time and receives the
positioning wireless signals from the plurality of wireless tags
such that the receptions of the positioning wireless signals are
staggered over time.
Thus, if the receiver is not able to receive the positioning
wireless signal from a wireless tag properly, the position of the
wireless tag is not updated, and the position obtained in the
process before the latest process is still stored for that wireless
tag.
Thus, if the interfering object moves during that time, there is a
possibility that the position of the interfering object may not be
measured properly even if the position of the interfering object is
measured based on respective positions of the plurality of wireless
tags as described above.
If the speed indicated by the deceleration command is set such that
the shorter a distance between the article transport vehicle and
the interfering object is, the lower the speed indicated by the
deceleration command is, then the distance between the article
transport vehicle and the interfering object cannot be calculated
properly if the position of the interfering object cannot be
measured properly as described above.
As a result, it may become impossible to set a proper speed as the
speed indicated by the deceleration command.
Incidentally, when the position of an interfering object is
measured using the positioning wireless signal from a single
wireless tag, there may be a difference between the position which
the wireless position measuring device measured as the position of
the interfering object and the actual position of the interfering
object.
However, the difference or the discrepancy with the actual position
would be relatively small compared with the case where the position
of an interfering object is measured by the multiple tag position
measurement process in which the positioning wireless signal from
one of the plurality of wireless tags associated with the
interfering object cannot be received.
Accordingly, in the above-described arrangement, both of the
multiple tag position measurement process in which the position of
each of the interfering objects is calculated based on the
positions of the plurality of wireless tags provided to each of the
interfering objects, and the single tag position measurement
process in which the position of each of the interfering objects is
calculated to be the position of one of the plurality of wireless
tags associated with the each of the interfering objects are
performed.
And the deceleration command is issued that indicates a slower
speed, between the deceleration command for the distance between
the article transport vehicle and the interfering object that is
calculated based on the position of the interfering object
calculated in the multiple tag position measurement process, and
deceleration command for the distance between the article transport
vehicle and the interfering object that is calculated based on the
position of the interfering object calculated in the single tag
position measurement process.
Thus, for example, when the positioning wireless signal from one of
the plurality of wireless tags associated with one of the
interfering objects cannot be received and the measured position of
the interfering object is different from its actual position, more
strict or conservative one of the deceleration commands is selected
as the deceleration command for the distance of between the article
transport vehicle and the interfering object.
Thus, interference between the article transport vehicle and an
interfering object can be avoided more reliably.
In an embodiment of the article transport facility in accordance
with the present invention, the position detector preferably is a
wireless position measuring device which preferably includes
wireless tags configured to output positioning wireless signals
which are wireless signals for position measurement, a plurality of
receivers configured to receive the positioning wireless signals
from the wireless tags that exist in the detection target area, and
a position calculation portion which calculates positions of the
wireless tags in the detection target area based on received
information from the plurality of receivers wherein the wireless
position measuring device performs a position measurement process
in which the position of the interfering object in the detection
target area is calculated, wherein a plurality of the wireless tags
are preferably provided to each of the interfering objects, wherein
the receiver is preferably configured to receive the positioning
wireless signal from only one of the wireless tags at one time and
to receive the positioning wireless signals from the plurality of
wireless tags such that the receptions of the positioning wireless
signals are staggered over time, wherein the wireless position
measuring device is preferably configured to measure the positions
of the interfering objects at every processing time by repeatedly
performing the position measurement process at every processing
time, and to perform, as the position measurement process, both of
a multiple tag position measurement process in which the position
of each of the interfering objects is calculated based on a
position of each of the plurality of wireless tags associated with
each of the interfering objects, and a single tag position
measurement process in which the position of each of the
interfering objects is calculated to be a position of one of the
plurality of wireless tags that are associated with the each of the
interfering objects, and wherein the external managing device is
preferably configured to issue the deceleration command if and when
at least one of; a distance, between the article transport vehicle
and the interfering object, calculated based on the position of the
interfering object calculated in the multiple tag position
measurement process; and a distance, between the article transport
vehicle and the interfering object, calculated based on the
position of the interfering object calculated in the single tag
position measurement process, becomes less than or equal to a
distance from the article transport vehicle to an outer edge of the
low speed area.
When the position of an interfering object is measured using
positioning wireless signals from a single tag, the calculation may
show a position that is different from the actual position of the
wireless tag as the position of the interfering object, depending
on the quality of the electromagnetic waves and on measurement
accuracy, among other factors.
For this reason, a plurality of the wireless tags are provided to
each of the interfering objects and the multiple tag position
measurement process is performed in which the position calculation
portion calculates the position of each of the plurality of the
wireless tags so that the position of the interfering object is
calculated based on the position of each of the plurality of
wireless tags.
This reduces the difference between the measured position and the
actual position to the extent possible so that the position of an
interfering object can be measured accurately.
As the multiple tag position measurement process, it is possible,
for example, to take an average of the positions of the plurality
of wireless tags.
In addition, the wireless position measuring device repeatedly
performs the position measurement process at every processing time,
and updates and stores the positions of the wireless tags obtained
in the latest process.
Thus, the position of the interfering object obtained in the latest
process may always be kept track of based on the positions of the
wireless tags obtained in the latest process.
However, each receiver can receive the positioning wireless signal
from only one of the wireless tags at one time and receives the
positioning wireless signals from the plurality of wireless tags
such that the receptions of the positioning wireless signals are
staggered over time.
Thus, if the receiver is not able to receive the positioning
wireless signal from a wireless tag properly, the position of the
wireless tag is not updated, and the position obtained in the
process before the latest process is still stored for that wireless
tag.
Thus, if the interfering object moves during that time, there is a
possibility that the position of the interfering object may not be
measured properly even if the position of the interfering object is
measured based on respective positions of the plurality of wireless
tags as described above.
If the speed indicated by the deceleration command is set such that
the shorter the distance between the article transport vehicle and
the interfering object is, the lower the speed indicated by the
deceleration command is, then the distance between the article
transport vehicle and the interfering object cannot be calculate
properly if the position of the interfering object cannot be
measured properly as described above.
As a result, it may become impossible to set a proper speed as the
speed indicated by the deceleration command.
Incidentally, when the position of an interfering object is
measured using the positioning wireless signal from a single
wireless tag, there may be a difference between the position which
the wireless position measuring device measured as the position of
the interfering object and the actual position of the interfering
object.
However, the difference or the discrepancy with the actual position
would be relatively small compared with the case where the position
of an interfering object is measured by the multiple tag position
measurement process in which the positioning wireless signal from
one of the plurality of wireless tags associated with the
interfering object can not be received.
Accordingly, with the above-described arrangement, both of the
multiple tag position measurement process in which the position of
each of the interfering objects is calculated based on the
positions of the plurality of wireless tags provided to each of the
interfering objects, and the single tag position measurement
process in which the position of each of the interfering objects is
calculated to be the position of one of the plurality of wireless
tags associated with the each of the interfering objects are
performed.
The deceleration command is issued if and when at least one of; the
distance, between the article transport vehicle and the interfering
object, calculated based on the position of the interfering object
calculated in the multiple tag position measurement process; and
the distance, between the article transport vehicle and the
interfering object, calculated based on the position of the
interfering object calculated in the single tag position
measurement process, becomes less than or equal to a distance from
the article transport vehicle to an outer edge of the low speed
area.
Thus, for example, when the positioning wireless signal from one of
the plurality of wireless tags associated with the interfering
object cannot be received and the measured position of the
interfering object is different from its actual position, more
strict or conservative distance is selected as the distance between
the article transport vehicle and the interfering object.
Thus, interference between the article transport vehicle and an
interfering object can be avoided more reliably.
In an embodiment of the article transport facility in accordance
with the present invention, preferably provided as the position
detector are a large area detector for detecting the position of
the interfering object in an entire area of the detection target
area, and a small area detector for detecting the position of the
interfering object in an area in the detection target area in which
it is difficult to detect the position of an interfering object
with the large area detector.
With the above-described arrangement, the large area detector
detects the position of an interfering object in an entire area of
the detection target area whereas the small area detector detects
the position of an interfering object in an area in the detection
target area in which it is difficult to detect the position of an
interfering object with the large area detector.
Thus, the configuration of the position detector can be simplified
compared with the case where the position of an interfering object
in the entire detection target area is detected by many small area
detectors.
Thus, the configuration of the position detector which can properly
detect an interfering object can be simplified.
In an embodiment of the article transport facility in accordance
with the present invention, the vehicle side travel controller is
preferably configured to change the normal travel speed to a lower
speed based on a travel condition, and to maintain the target
travel speed at the normal travel speed even if the deceleration
command is issued from the ground side travel controller while the
target travel speed is set to the normal travel speed if the normal
travel speed is less than the reduced travel speed.
With the above-described arrangement, the normal travel speed is
changed to a lower speed based on a travel condition (e.g., shaped
of the travel path or the weight of the load when traveling), the
article transport vehicle can travel at a speed suitable for the
given travel condition.
And when the normal travel speed is less than the reduced travel
speed, the target travel speed is maintained at the normal travel
speed even if the deceleration command is issued; so, the speed
suitable for the travel condition can be maintained without being
changed to the reduced travel speed that is greater than the speed
suitable for the travel condition.
In an embodiment of the article transport facility in accordance
with the present invention, the article transport vehicle
preferably includes a presence detector for detecting a presence of
the interfering object located forwardly in the travel direction of
the article transport vehicle, and an auxiliary travel controller
which controls operation of the travel actuating device based on
the detected information from the presence detector.
And the auxiliary travel controller is preferably configured to
change the travel speed of the article transport vehicle from the
normal travel speed to a reduced travel speed which is less than
the normal travel speed if and when the interfering object is
detected by the presence detector while the target travel speed is
set to the normal travel speed.
With the above-described arrangement, if and when a presence of an
article is detected by the presence detector, the auxiliary travel
controller changes the travel speed of the article transport
vehicle to the reduced travel speed.
As such, in addition to when the position detector detects the
position of an interfering object, the travel speed of the article
transport vehicle can be changed from the normal travel speed to
the reduced travel speed when a presence of the interfering object
is detected by the presence detector.
Thus, even if one of the detectors fails, an interfering object can
be detected by the other detector, so that an interfering object
can be detected by a detector more properly and reliably.
In an embodiment of the article transport facility in accordance
with the present invention, the position detector is preferably
configured to transmit interfering object presence information to
the presence detector if and when the distance from the article
transport vehicle to the interfering object becomes less than or
equal to a deceleration distance defined in advance, based on
position information of the detected interfering object and travel
position information for the article transport vehicle.
And the presence detector is preferably configured to be changed to
a detection state in which a presence of the interfering object is
detected, upon receiving the interfering object presence
information from the said position detector.
With the above-described arrangement, the position detector
transmits interfering object presence information to the presence
detector if and when the distance from the article transport
vehicle to the interfering object becomes less than or equal to the
deceleration distance defined in advance.
And upon receiving interfering object presence information from the
position detector, the presence detector is changed to the
detection state even if the presence detector has not detected the
presence of the object. When the presence detector is thus changed
to the detection state, the auxiliary travel controller changes the
travel speed of the article transport vehicle from the normal
travel speed to the reduced travel speed.
Therefore, when the position detector detects the position of an
interfering object, the travel speed of the article transport
vehicle is changed from the normal travel speed to the reduced
travel speed in two ways, namely, changing the travel speed of the
article transport vehicle from the normal travel speed to the
reduced travel speed by the external managing device and the
vehicle side travel controller, and changing the travel speed of
the article transport vehicle from the normal travel speed to the
reduced travel speed by the presence detector and the auxiliary
travel controller.
Therefore, for example, even if a situation occurs in which the
target travel speed cannot be changed to the reduced travel speed
in one way, the travel speed of the article transport vehicle can
be changed to the reduced travel speed in another way. Thus, the
target travel speed can be changed to the reduced travel speed more
precisely and reliably.
In an embodiment of the article transport facility in accordance
with the present invention, the external managing device is
preferably configured to be able to determine a kind of interfering
object based on detected information from the position detector,
and to set a predefined low speed distance differently depending on
the kind of interfering object.
With the above-described arrangement, the low speed distance can be
set differently (i.e., set to different distances) depending on the
kind of interfering object. Thus, the low speed distance can be set
in accordance with the nature of the interfering object.
For example, when the interfering object is a human worker, a
longer low speed distance may be used since it is possible that the
worker may start to walk toward the article transport vehicle.
And when the interfering object is an article placed on the floor,
a shorter low speed distance may be used because the article does
not move.
Thus, the number of times that the article transport vehicle is
decelerated can be reduced and the articles can be transported more
efficiently by selecting a shorter low speed distance for an
interfering object for which the possibility of interference is
small.
And a longer low speed distance may be selected for an interfering
object with a greater possibility of interference in order to
reliably prevent the article transport vehicle from interfering
with the interfering object.
In an embodiment of the article transport facility in accordance
with the present invention, the external managing device is
preferably configured to be able to set a low speed distance
defined in advance for when the interfering object is located
forwardly of the article transport vehicle in the travel direction
to be different from the low speed distance defined in advance for
when the interfering object is located rearwardly of the article
transport vehicle in the travel direction.
With the above-described arrangement, the low speed distance can be
set differently for when an interfering object is located forwardly
of the article transport vehicle in the travel direction and for
when it is located rearwardly of the article transport vehicle in
the travel direction.
Thus, for example, for the forward side in the travel direction
which is the direction of movement of the article transport
vehicle, a longer low speed distance may be selected since it is
easier to interfere with an interfering object.
And for the rearward side in the travel direction which is not the
direction of movement of the article transport vehicle, a shorter
low speed distance may be selected since it is more difficult to
interfere with an interfering object.
Thus, the number of times that the article transport vehicle is
decelerated can be reduced and the articles can be transported more
efficiently by selecting a shorter low speed distance for the side
that has a lower possibility of interference between the forward
side and the rearward side in the travel direction.
And a longer low speed distance may be selected for the side with a
greater possibility of interference in order to reliably prevent
the article transport vehicle from interfering with the interfering
object.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view of an article transport facility,
FIG. 2 is a control block diagram for the article transport
facility,
FIG. 3 is a perspective view of an article transport vehicle,
FIG. 4 is a time chart which shows how the target travel speed of
the article transport vehicle is changed,
FIG. 5 shows areas used in changing the target travel speed of the
article transport vehicle,
FIG. 6 is a time chart which shows changes in the target travel
speed of the article transport vehicle (high speed, low load),
FIG. 7 is a time chart which shows changes in the target travel
speed of the article transport vehicle (low speed, high load),
FIG. 8 is a perspective view showing a detection area,
FIG. 9 is a time chart which shows changes in the target travel
speed of the article transport vehicle (high speed, low load),
FIG. 10 is a flow chart of a process which an external managing
device performs based on a position measurement process of the
first embodiment,
FIG. 11 is a flow chart of a process which the external managing
device performs based on the position measurement process of the
second embodiment,
FIG. 12 is a flow chart of a process which the external managing
device performs based on the position measurement process of the
second embodiment,
FIG. 13 shows areas used in changing the target travel speed of the
article transport vehicle of an alternative embodiment, and
FIG. 14 shows areas used in changing the target travel speed of the
article transport vehicle in accordance with yet another
alternative embodiment.
DETAILED DESCRIPTION
First Embodiment
The first embodiment in accordance with the present invention is
described next with reference to the drawings.
As shown in FIG. 1, an article transport facility includes a
plurality of stations S, each of which functions as an article
transfer location provided at a side of the travel path L, and an
article transport vehicle 1 configured to travel on the floor and
along the travel path L extending by way of or along a plurality of
stations S.
And the article transport vehicle 1 travels autonomously along the
travel path L to transport articles (i.e. pallets as well as goods
and things received and supported by the pallets) among the
plurality of stations S one article at a time.
In addition, in the article transport facility, workers 2 from
outside walk on the floor and a fork lift truck 3, operated by the
driver in the fork lift truck 3, also travels on the floor.
While the travel path L is shown with solid lines in FIG. 1, it
only represents a virtual travel path along which the article
transport vehicle 1 should travel. And no rail is installed for
guiding the article transport vehicle 1.
As shown in FIG. 2, the article transport vehicle 1 includes a
travel motor 5 for drivingly rotating driven travel wheels (not
shown), and a steering motor 6 for allowing freely rotatable travel
wheels (not shown) to be rotated about a vertical axis (axis
extending along a vertical direction) and for changing the
direction of freely rotatable travel wheels.
The article transport vehicle 1 is configured to travel as the
travel motor 5 drivingly rotates the driven travel wheels and to
change its travel direction as the steering motor 6 changes the
direction of freely rotatable travel wheels.
The travel motor 5 and the steering motor 6 define a travel
actuating device 7 whereby the article transport vehicle 1 is
configured to be able to travel along the travel path L by the
operation of the travel actuating device 7.
As shown in FIG. 3, the article transport facility includes a
plurality of reflecting plates 9 that are located at positions that
correspond to the travel path L, using walls among other things
that are located to one or both sides of the travel path L.
Provided in an upper portion of the article transport vehicle 1 is
a light emitter-receiver 10 that emits Laser light in sweeping
motions in a horizontal plane and that receives the reflected light
reflected by the reflecting plates 9.
In addition, the article transport vehicle 1 includes a distance
detector 11 for detecting, or measuring, travel distance, such as a
rotary encoder, etc., that outputs pulse signals as the driven
travel wheel is rotated, and a direction detector 12 such as a rate
gyro that detects the direction of the article transport vehicle
1.
The emitter-receiver 10, the distance detector 11, and the
direction detector 12 define a travel position detector 13 for
detecting the travel position of the article transport vehicle
1.
The travel position detector 13 is mounted on, or is provided to,
the article transport vehicle 1.
As shown in FIG. 2, a vehicle side controller H1 that functions as
a vehicle side travel controller for controlling the operation of
the travel actuating device 7 is provided to the article transport
vehicle 1.
The vehicle side controller H1 is configured to control the
operation of the travel actuating device 7, based on travel
position information detected by the travel position detector 13
and travel command information from the ground side controller H2
which functions as a ground side travel controller, in order to
cause the article transport vehicle 1 to travel toward a target
travel position along the travel path L at a target travel
speed.
More specifically, the vehicle side controller H1 is configured to
confirm, verify, or otherwise determine the current position of the
article transport vehicle 1 based on sweep angle information of the
reflected light received by the emitter-receiver 10 and position
information on the plurality of reflecting plates 9, and to control
the operation of the travel motor 5 and the steering motor 6 to
cause the article transport vehicle 1 to travel along the travel
path L at a target travel speed to the target travel position that
corresponds to the station S indicated by, or specified in, a
travel command issued from the ground side controller H2 based on
the current position information, the detected information from the
distance detector 11, and the detected information from the
direction detector 12.
The travel path L is an imaginary path along which the article
transport vehicle 1 should travel as described above.
Path information of the travel path L is stored in the vehicle side
controller H1 as map data. And when a travel command is issued, the
vehicle side controller H1 determines a route along the travel path
L.
As shown in FIG. 4, defined as the normal travel speed in the
vehicle side controller H1 are a high travel speed for when the
article transport vehicle 1 travels in a straight path portion of
the travel path L, a intermediate travel speed for when the article
transport vehicle 1 travels in a curved path portion of the travel
path L, and a creep travel speed.
In addition, a travel speed when traveling under a low load
condition as well as a travel speed when traveling under a high
load condition are defined for each of the high travel speed and
the intermediate travel speed.
Incidentally, in the present embodiment, the high travel speed
under a low load condition is set to be 200 m/min, the high travel
speed under a high load condition is set to be 160 m/min, the
intermediate travel speed under a low load condition is set to be
60 m/min, the intermediate travel speed under a high load condition
is set to be 40 m/min, and the creep travel speed is set to be 5
m/min.
Thus, these speeds are defined so that they decrease in the order
from the high travel speed under a low load condition, the high
travel speed under a high load condition, the intermediate travel
speed under a low load condition, the intermediate travel speed
under a high load condition, and to the creep travel speed.
Note that traveling under a low load condition means that the
article transport vehicle is traveling with no load, i.e., with the
article transport vehicle supporting no articles.
And traveling under a high load condition means that the article
transport vehicle is traveling with load, i.e., with the article
transport vehicle supporting an article.
Thus, the vehicle side controller H1 is configured to reduce the
normal travel speed to a lower speed based on a travel condition
(shape of the travel path L, and/or whether an article is being
transported) in order to set the target travel speed to a speed
less than the high travel speed when the article transport vehicle
1 travels in a curved portion of the travel path L or under the
high load condition, with respect to the high travel speed for when
the article transport vehicle 1 travels in a straight path portion
in the travel path L under the low load condition.
And as shown in FIG. 4, when causing the article transport vehicle
1 to travel along the travel path L, the vehicle side controller H1
is configured to control the operation of the travel actuating
device 7 in order to cause the article transport vehicle 1 to:
travel with the target travel speed set to the high travel speed
when traveling in a straight path portion; to travel with the
target travel speed set to the intermediate travel speed when
traveling in a curved path portion; and to stop at the target
travel position after causing it to decelerate to the creep travel
speed.
FIG. 4 shows the target travel speed when the article transport
vehicle 1 under the low load condition travels in a straight path
portion, a curved path portion, and then a straight path portion in
that order.
In addition, as shown in FIG. 2, the article transport vehicle 1 is
provided with an interfering object sensor 15 which functions as a
presence detector for detecting the presence of an interfering
object located forwardly of the article transport vehicle 1 in the
travel direction thereof, a sensor controller 16 which functions as
an auxiliary travel controller for controlling the operation of the
travel actuating device 7 based on the detected information from
the interfering object sensor 15, a bumper sensor 26 for detecting
that an interfering object has contacted a bumper of the article
transport vehicle 1, a power source 17 (battery) for supplying
electric power to the travel actuating device 7 (the travel motor 5
and the steering motor 6), and an electric-power interrupting
device 18 which can interrupt supply of the electric power from the
power source 17 to the travel actuating device 7.
Incidentally, an interfering object which the interfering object
sensor 15 and the bumper sensor 26 detect is any object that has a
possibility of interfering, colliding, or contacting the article
transport vehicle 1, such as a human worker 2, a fork lift truck 3,
or an article placed on the floor.
The sensor controller 16 is incorporated within the interfering
object sensor 15 and is configured to determine the distance from
the article transport vehicle 1 to the interfering object based on
the detected information from the interfering object sensor 15 if
and when the presence of an interfering object is detected by the
interfering object sensor 15.
In addition, a wall may be installed laterally of the travel path
L. Or an article storage rack may be installed on the floor such
that it would not interfere with the article transport vehicle 1
traveling along the travel path L.
Or an article may be placed directly on the floor.
The positions of the interfering objects currently installed on the
floor such as a wall or a rack, and the positions of the
interfering objects that are scheduled to be placed on the floor
are stored in the sensor controller 16 in advance as a layout
map.
And even if the interfering object sensor 15 detects an interfering
object whose position is stored in advance, the sensor controller
16 is configured to cancel or nullify the detected information, and
is configured not to determine that an interfering object is
present.
And if and when a presence of an interfering object is detected by
the interfering object sensor 15 while the target travel speed is
set to the normal travel speed, the sensor controller 16 is
configured to cause the article transport vehicle 1 to decelerate
either by reducing the speed upper limit for the target travel
speed set by the vehicle side controller H1 or by interrupting the
supply of the electric power to the travel actuating device 7 with
the electric-power interrupting device 18, depending on the
distance from the article transport vehicle 1 to the interfering
object that is determined based on the detected information, to
perform an emergency stop.
To describe in more detail, as shown in FIG. 5, a long distance (20
m), an intermediate distance (8 m) which is shorter than the long
distance, and a short distance (2 m) which is shorter than the
intermediate distance are defined in advance as the deceleration
distances in the sensor controller 16.
And defined in advance as low speed areas for a small area detector
are fan-shaped areas (i.e., wedge-shaped circular sections) that
spread forwardly of the article transport vehicle 1, each of which
has its center at the position of the article transport vehicle 1,
and whose radii are equal to respective deceleration distances
defined above, namely, a fan-shaped area (area A1) whose radius is
equal to the long distance, a fan-shaped area (area A2) whose
radius is equal to the intermediate distance, and a fan-shaped area
(area A3) whose radius is equal to the short distance.
And the sensor controller 16 is configured to transmit long
distance approach information to the vehicle side controller H1 if
and when an interfering object has entered the area A1 and the
distance from the article transport vehicle 1 to the interfering
object is less than or equal to the long distance and is greater
than the intermediate distance.
And the sensor controller 16 is configured to transmit intermediate
distance approach information to the vehicle side controller H1 if
and when the interfering object has entered the area A2 and the
distance from the article transport vehicle 1 to the interfering
object is less than or equal to the intermediate distance and is
greater than the short distance.
And if and when the interfering object has entered the area A3 and
the distance from the article transport vehicle 1 to the
interfering object is less than the short distance, the sensor
controller 16 is configured to control the operation of the
electric-power interrupting device 18 in order to cause the
electric-power interrupting device 18 to interrupt the electric
power to the travel actuating device 7 and to cause the article
transport vehicle 1 to perform an emergency stop.
As shown in FIG. 6 FIG. 7, a first upper limit speed (60 m/min)
which is less than the high travel speed and is equal to the medium
traveling speed and a second upper limit speed (30 m/min) which is
less than the intermediate travel speed are defined in the vehicle
side controller H1 as reduced travel speeds.
And the vehicle side controller H1 is configured to set the upper
speed limit for the target travel speed to be the first upper limit
speed when the long distance approach information is received from
the sensor controller 16, and to set the upper speed limit for the
target travel speed to be the second upper limit speed when the
intermediate distance approach information is received from the
sensor controller 16.
Thus, for example, as shown in FIG. 6, if and when the upper speed
limit for the target travel speed is restricted to the first upper
limit speed or the second upper limit speed while the article
transport vehicle 1 is traveling at the high travel speed (under a
low load condition), the target travel speed of the article
transport vehicle 1 is set to the upper speed limit, i.e., either
the first upper limit speed or the second upper limit speed.
Thus, the vehicle side controller H1 is configured to change the
target travel speed from the normal travel speed to the reduced
travel speed if and when a deceleration command is issued from the
sensor controller 16, i.e., if and when the long distance approach
information or intermediate distance approach information is
received, while the target travel speed is set to a normal travel
speed.
In addition, for example, as shown in FIG. 7, when the article
transport vehicle 1 is traveling at the intermediate travel speed
(under a high load condition), the target travel speed for the
article transport vehicle 1 is not changed from the intermediate
travel speed even if the upper speed limit of the target travel
speed is restricted to the first upper limit speed.
And when the upper speed limit for the target travel speed is
restricted to the second upper limit speed, the target travel speed
for the article transport vehicle 1 is changed to the upper speed
limit, namely, the second upper limit speed.
As such, when the normal travel speed is less than the reduced
travel speed, the vehicle side controller H1 is configured to
maintain the target travel speed at the normal travel speed even if
a deceleration command is issued from the sensor controller 16
while the target travel speed is set at the normal travel
speed.
The bumper sensor 26 is incorporated within the bumper of the
article transport vehicle 1 and is a tape switch.
And the electric-power interrupting device 18 interrupts the
electric power to the travel actuating device 7 if and when the
bumper sensor 26 detects that an interfering object contacted the
bumper.
A ground side controller H2 which issues travel commands to the
article transport is provided on the ground side within the article
transport facility.
And a transmitter-receiver 14 for mutually transmitting and
receiving a variety of information is provided to each of the
vehicle side controller H1 and the ground side controller H2. Here,
an item being provided "on the ground side" means that the item is
not provided to the article transport vehicle 1 but is provided on
the floor or the ceiling of the article transport facility, or to
an object such as an article storage rack, etc., which is installed
in the article transport facility.
And the ground side controller H2 is configured to transmit to the
vehicle side controller H1 a travel command which specifies the
station S of transport origin from which an article is to be
transported and the station S of transport destination.
The vehicle side controller H1 is configured to control the
operation of the travel actuating device 7 based on travel position
information and travel command information, and to the transmit
travel position information of the article transport vehicle 1 to
the ground side controller H2.
In addition, provided on the ground side of the article transport
facility are position detectors 19 for detecting the positions of
interfering objects that may exist in a detection target area E
which includes the area in which the travel path L is installed,
and an external management server H3 which functions as an external
managing device which issues a deceleration command to the article
transport vehicle 1 if and when the distance from the article
transport vehicle 1 to an interfering object becomes less than or
equal to a low speed distance based on position information of the
interfering object from the position detector 19 and travel
position information for the article transport vehicle 1.
As shown in FIGS. 1 and 8, provided as the position detectors 19
are a wireless position measuring system 21 which functions as a
large area detector for detecting the position of an interfering
object in the entire detection target area E, and a monitoring
camera 20 which functions as a small area detector for detecting
the position of an interfering object in an area (detection area e)
within the detection target area E in which it is difficult to
detect the position of an interfering object with the large area
detector.
An Axi-Vision camera (a three-dimensional distance-mapping imaging
camera) is provided as the monitoring camera 20.
The wireless position measuring system 21 includes wireless tags 22
which are carried by workers 2 and the fork lift truck 3 and which
are configured to output positioning wireless signals which are
wireless signals for position measurement, a plurality of base
units 23 configured to receive the positioning wireless signals
from the wireless tags 22 in the detection target area E, and a tag
position measuring device 24 for performing a position measurement
process in which the position of each wireless tag 22 is calculated
based on the information received by the base units 23.
The information for position measurement can be communicated from
each wireless tag 22 to a base unit 23 by wireless communication
using the UWB (Ultra-Wide Band) technology.
Thus, the wireless position measuring system 21 corresponds to the
wireless position measuring device in the present invention, and
the tag position measuring device 24 corresponds to the position
calculation portion in the present invention.
In addition, in the present embodiment, a plurality of receivers
provided to the wireless position measuring system 21 are the
plurality of base units 23.
Incidentally, as shown in FIG. 1, four base units 23 are provided
such that one base unit 23 is located at each of the four corners
of the detection target area E.
The interfering objects which the wireless position measuring
system 21 detects, are the worker 2 and the fork lift truck 3 each
carrying the wireless tags 22.
And the wireless position measuring system 21 is configured to
transmit position information of the detected interfering object to
the external management server H3.
Incidentally, objects without the wireless tags 22, such as an
article, are not detected as interfering objects.
And attribute information about the object carrying the wireless
tags 22 is transmitted in the information transmitted from the
wireless tag 22.
And the wireless position measuring system 21 is configured to
determine the attribute (i.e., a worker 2 or the fork lift truck 3)
of the interfering object carrying the wireless tags 22 from the
information from the wireless tags 22.
Each worker 2 carries two wireless tags 22 and each fork lift truck
3 carries two wireless tags 22.
In the present embodiment, the wireless position measuring system
21 keeps track of, or manages, the total number of the wireless
tags 22 that exist in the detection target area E as well as
identifying information for every wireless tag 22 that exists in
the detection target area E. (The managing portion that manages the
identifying information may be provided to the base units 23, or to
the tag position measuring device 24.) And polling wireless signals
are transmitted all at once to each of the wireless tags 22 that
exist in the detection target area E in sequence in a predetermined
polling order.
The polling wireless signals are transmitted all at once from the
four base units 23.
Each wireless tag 22 that receives the polling wireless signal
transmits a positioning wireless signal as a response. This
positioning wireless signal is received by two or more base units
23 out of the four base units 23.
And the tag position measuring device 24 uses a known positioning
scheme, such as TDOA and TOA, to calculate the position of the
wireless tag 22.
In addition, for the pair of wireless tags 22 carried by the same
interfering object, the tag position measuring device 24 calculates
their positions serially and in succession.
More specifically, each receiver is configured such that it can
receive the positioning wireless signal from only one wireless tag
22 at a time and receives the positioning wireless signals from a
plurality of wireless tags 22 such that the signal receptions are
spread or staggered over time.
The wireless position measuring system 21 is configured to
calculate the positions of the wireless tags 22 one by one at every
predetermined cycle in the polling order mentioned above, and to
perform a position measurement process in which the position of an
interfering object is measured, or determined, based on the
calculated positions of the wireless tags 22.
The predetermined cycle mentioned above is defined to be an amount
of time in which the positions can be calculated for the maximum
number of the wireless tags 22 that can exist in the detection
target area E.
In the present embodiment, the predetermined cycle is, or
corresponds to, the processing time.
When the positions of all the wireless tags 22 that exist in the
detection target area E are calculated, the wireless position
measuring system 21 returns to the beginning of the polling order
and continues to transmit the polling wireless signals.
Thus, the wireless position measuring system 21 is configured to
measure the positions of the workers 2 and the fork lift truck 3 at
every processing time by repeatedly performing the position
measurement process at every processing time.
If the monitoring camera 20 detects movement of any object in the
detection area e by comparing image information captured most
recently with image information captured in the past, the
monitoring camera 20 is configured to determine the object that has
moved to be an interfering object.
In addition, image information of the article transport vehicle 1
is stored in the monitoring camera 20 in advance.
And if the monitoring camera 20 determines that the object that has
moved is the article transport vehicle 1, the monitoring camera 20
is configured to cancel, or nullify, the detected information for
the moving object, and is configured not to determine that an
interfering object exists.
And the monitoring camera 20 is configured to derive the distance
from the article transport vehicle 1 to the interfering object from
the position information for the article transport vehicle 1
transmitted from the external management server H3 and the position
information for the detected interfering object, and to transmit
the distance information from the article transport vehicle 1 to
the interfering object to the external management server H3.
Incidentally, the travel position information for the article
transport vehicle 1 is transmitted to the external management
server H3 from the ground side controller H2.
And the travel position information is transmitted from the
external management server H3 to the monitoring camera 20.
The external management server H3 is configured to be able to set
the low speed distance, for when an interfering object is located
forwardly of the article transport vehicle 1 in the travel
direction, to be different from the low speed distance for when an
interfering object is located rearwardly of the article transport
vehicle 1 in the travel direction.
And in the present embodiment, a remote distance (25 m) and a
neighboring distance (15 m) which is shorter than the remote
distance are defined in the external management server H3 as the
low speed distances for the large area detector for when an
interfering object is located forwardly of the article transport
vehicle 1 in the travel direction.
And defined in the external management server H3 as the low speed
areas for the large area detector for when an interfering object is
located forwardly of the article transport vehicle 1 in the travel
direction are a semi-circular area (area D1) which has its center
at the position of the article transport vehicle 1, which spreads
forwardly of the article transport vehicle 1, and whose radius is
equal to the remote distance, and a semi-circular area (area D2)
which has its center at the position of the article transport
vehicle 1, which spreads forwardly of the article transport vehicle
1, and whose radius is equal to the neighboring distance.
In addition, the low speed distance is set to be 0 m for when an
interfering object is located rearwardly of the article transport
vehicle 1.
Thus, the low speed distance for when an interfering object is
located rearwardly of the article transport vehicle 1 can be set to
be less than the low speed distance for when an interfering object
is located forwardly of the article transport vehicle 1.
Incidentally, the remote distance is set to be greater than the
long distance and the neighboring distance is set to be less than
the long distance, and greater than the intermediate distance.
And the external management server H3 is configured to transmit
remote approach information to the ground side controller H2 if and
when an interfering object has entered the area D1 and the distance
from the article transport vehicle 1 to the interfering object is
less than or equal to the remote distance and is greater than the
neighboring distance, based on the position information for the
interfering object transmitted from the monitoring camera 20 or the
wireless position measuring system 21 and the travel position
information for the article transport vehicle 1 from the ground
side controller H2, and is configured to transmit neighboring
approach information to the ground side controller H2 if and when
the interfering object has entered the area D2, and the distance
from the article transport vehicle 1 to the interfering object
becomes less than or equal to the neighboring distance.
When the remote approach information and the neighboring approach
information are received from the external management server H3,
the ground side controller H2 is configured to transmit, or
forward, the remote approach information and the neighboring
approach information to the vehicle side controller H1.
And the vehicle side controller H1 is configured to set the upper
speed limit for the target travel speed to be the first upper limit
speed when it receives the remote approach information from the
sensor controller 16, and to set the upper speed limit for the
target travel speed to be the second upper limit speed when it
receives the neighboring approach information from the sensor
controller 16.
And if and when a deceleration command is issued from the external
management server H3 (i.e. if and when the remote approach
information or the neighboring approach information is received)
while the target travel speed is set to be a normal travel speed,
the vehicle side controller H1 is configured to set the target
travel speed to be the reduced travel speed that is less than the
normal travel speed.
That is, several different distances are defined as low speed
distances.
And the external management server H3 is configured to set the
speed as indicated by the deceleration command such that the
shorter the distance between the article transport vehicle 1 and an
interfering object with respect to the low speed distance is, the
lower the speed is set.
As shown in FIG. 5, the monitoring camera 20 is provided with a
camera control portion (not shown) in which a long distance (20 m),
an intermediate distance (8 m) which is shorter than the long
distance, and a short distance (2 m) which is shorter than the
intermediate distance are defined in advance as deceleration
distances, which are identical to those defined for the sensor
controller 16.
The monitoring camera 20 is configured such that command
information can be wirelessly communicated from the monitoring
camera 20 to the sensor controller 16.
And defined as the low speed areas for the small area detector are
fan-shaped areas whose radii are equal to respective deceleration
distances defined above, namely, a fan-shaped area (area A1) whose
radius is equal to the long distance, a fan-shaped area (area A2)
whose radius is equal to the intermediate distance, and a
fan-shaped area (area A3) whose radius is equal to the short
distance.
In other words, in the present embodiment, each of area A1, area
A2, area A3, area D1 area, and area D2 is defined in advance as the
low speed areas.
And the low speed areas are defined to have their respective radii
equal to the predetermined deceleration distances and to be
fun-shaped areas which share the same center at the position of the
article transport vehicle 1 and spread forwardly of the article
transport vehicle 1, in plan view.
An outer edge of a given low speed area is a portion which forms
the arc of the low speed area.
In addition, the monitoring camera 20 is configured to be able to
transmit command information to the sensor controller 16 for the
interfering object sensor 15.
And the monitoring camera 20 is configured: to issue a first
deceleration command to the sensor controller 16 if the distance
from the article transport vehicle 1 to an interfering object is
less than or equal to the long distance and is greater than the
intermediate distance; to issue a second deceleration command to
the sensor controller 16 if the distance from the article transport
vehicle 1 to the interfering object is less than or equal to the
intermediate distance and is greater than the short distance; and
to issue a third deceleration command to the sensor controller 16
if the distance from the article transport vehicle 1 to the
interfering object is less than or equal to the short distance.
And even if the presence of an interfering object is not detected
by the interfering object sensor 15, the sensor controller 16 is
configured to be forced to be in a detection state in which the
distance from the article transport vehicle 1 to an interfering
object is deemed to be less than or equal to the long distance and
greater than the intermediate distance if and when the first
deceleration command is issued from the monitoring camera 20, and
to transmit long distance approach information to the vehicle side
controller H1, and also to be forced to be in a detection state in
which the distance from the article transport vehicle 1 to an
interfering object is deemed to be less than or equal to the
intermediate distance and greater than the short distance if and
when the second deceleration command is issued from the monitoring
camera 20, and to transmit intermediate distance approach
information to the vehicle side controller H1.
In addition, even if the presence of an interfering object is not
detected by the interfering object sensor 15, the sensor controller
16 is configured to be forced to be in a detection state in which
the distance from the article transport vehicle 1 to an interfering
object is deemed to be less than or equal to the short distance if
and when the third deceleration command is issued from the
monitoring camera 20, and to control the operation of the
electric-power interrupting device 18 in order to interrupt the
electric power to the travel actuating device 7 with the
electric-power interrupting device 18 to cause the article
transport vehicle 1 to perform an emergency stop.
Thus, the sensor controller 16 is configured to switch to a
detection state in which the presence of an interfering object is
deemed to be detected upon receiving interfering object presence
information from the monitoring camera 20.
In addition, if and when an interfering object is detected by the
monitoring camera 20 while the target travel speed is set to the
normal travel speed, the sensor controller 16 is configured to
transmit the long distance approach information or the intermediate
distance approach information to the vehicle side controller H1 to
change the travel speed of the article transport vehicle 1 from the
normal travel speed to the reduced travel speed, namely, the first
upper limit speed or the second upper limit speed, or to control
the operation of the electric-power interrupting device 18 on its
own in order to change the travel speed of the article transport
vehicle 1 from the normal travel speed to a reduced travel speed
for a stop speed.
The long distance approach information and intermediate distance
approach information are transmitted from the sensor controller 16
to the vehicle side controller H1, whereas the remote approach
information and the neighboring approach information are
transmitted from the external management server H3 to the vehicle
side controller H1.
And when the article transport vehicle 1 travels toward an
interfering object while traveling at a high travel speed (under
the low load condition), and as the interfering object enters the
area D1, area A1, area D2, and area A2 in that order and shown in
FIG. 5, the upper limit speed is changed as follows.
As shown in FIG. 9, the vehicle side controller H1 changes the
upper speed limit for the target travel speed to the first upper
limit speed if and when the interfering object enters the area D1
and the remote approach information is transmitted from the ground
side controller H2, and maintains the upper speed limit for the
target travel speed at the first upper limit speed if and when the
interfering object enters the area A1 and the long distance
approach information is transmitted from the sensor controller
16.
In addition, the vehicle side controller H1 changes the upper speed
limit for the target travel speed to the second upper limit speed
if and when the interfering object enters the area D2 and the
neighboring approach information is transmitted from the ground
side controller H2, and maintains the upper speed limit speed for
the target travel speed at the second upper limit speed if and when
the interfering object enters the area A2 and the short distance
approach information is transmitted from the sensor controller
16.
Incidentally, subsequently, if and when the interfering object
enters the area A3, the sensor controller 16 controls the operation
of the electric-power interrupting device 18 to interrupt the
electric power to the travel actuating device 7 to cause the
article transport vehicle 1 to perform an emergency stop.
Thus, to the vehicle side controller H1, the long distance approach
information and intermediate distance approach information are
transmitted from the sensor controller 16 whereas the remote
approach information and neighboring approach information are
transmitted from the external management server H3.
And between the long distance approach information and intermediate
distance approach information, the target travel speed is
restricted or reduced based on the approach information that is
received later of the two. Also between the remote approach
information and neighboring approach information, the target travel
speed is restricted or reduced based on the approach information
that is received later of the two. And between the approach
information from the sensor controller 16 and the approach
information from the external management server H3, the approach
information that leads to the lower upper speed limit is given
priority when restricting, or reducing, the target travel
speed.
And, as shown in FIG. 8, an interfering object may exist in an area
in which the object is hard to detect with the wireless position
measuring system 21 or with the interfering object sensor 15.
With such hard-to-detect area chosen as the detection area e, the
monitoring camera 20 is provided in order to detect the position of
an interfering object which exists in the detection area e.
Thus, even if an interfering object that exists in the detection
area e cannot be detected by the wireless position measuring system
21 or by the interfering object sensor 15, the target travel speed
for the article transport vehicle 1 can be changed based on the
detected information from the monitoring camera 20 as shown in
FIGS. 6 and 7.
And changing the target travel speed for the article transport
vehicle 1 based on the detected information from the monitoring
camera 20 can be performed based firstly on information transmitted
to the vehicle side controller H1 through the external management
server H3 and the ground side controller H2, and secondly on
information that is wirelessly transmitted from the monitoring
camera 20 to the sensor controller 16 and that is then transmitted
from the sensor controller 16 to the vehicle side controller
H1.
Thus, there are two routes for the transmission of the information,
which improves the reliability of the target travel speed
change.
In addition, in the present embodiment, the wireless position
measuring system 21 is configured to perform: a multiple tag
position measurement process in which a midpoint between the
positions of a pair of wireless tags 22 associated with, or carried
by, each worker 2 or by each fork lift truck 3 is calculated and
derived as the position of the worker 2 or the fork lift truck 3;
and a single tag position measurement process in which the position
of one of the pair of wireless tags 22 associated with, or carried
by, each worker 2 or by each fork lift truck 3 is calculated and
derived as the position of the worker 2 or the fork lift truck
3.
In the single tag position measurement process, of the two wireless
tags 22 carried by one interfering object, the position of the
wireless tag 22 that is behind the other in the polling order is
selected to be the position of the interfering object as the
position information for the wireless tag 22 that more accurately
reflects the actual position of the moving interfering object (a
worker 2 or a fork lift truck 3).
If the positioning wireless signal cannot be received from one of
the wireless tags 22 carried by the interfering object of 1, the
position of the wireless tag 22 from which the positioning wireless
signal can be received is deemed to be the position of the
interfering object.
The processes which the external management server H3 performs
based on the position measurement process performed by the wireless
position measuring system 21 is described next with reference to
the flow chart in FIG. 10.
The external management server H3 commands the tag position
measuring device 24 of the wireless position measuring system 21 to
calculate the positions of the two wireless tags 22 associated
with, or carried by, the worker 2 or the fork lift truck 3 (Step
#101).
The external management server H3 next commands the wireless
position measuring system 21 to measure, as the multiple tag
position measurement process, the position of the midpoint of the
two wireless tags 22 as the position of the worker 2 or the fork
lift truck 3 (Step #102).
And the external management server H3 then calculates a multiple
tag determination distance which is the distance between the worker
2 or the fork lift truck 3 and the article transport vehicle 1
based on the measured position of the worker 2 or the fork lift
truck 3 (Step #103).
The external management server H3 determines if the multiple tag
determination distance is less than or equal to the remote distance
and greater than the neighboring distance, or is less than or equal
to the neighboring distance (see FIG. 5), and sets the first upper
limit speed as a deceleration command speed for the multiple tag
determination distance if it is less than or equal to the remote
distance and greater than the neighboring distance, and sets the
second upper limit speed as the deceleration command speed for the
multiple tag determination distance if it is less than or equal to
the neighboring distance, and stores it in a temporary memory (Step
#104).
The external management server H3 next commands the wireless
position measuring system 21 to measure, as the single tag position
measurement process, the position of one of the two wireless tags
22 as the position of the worker 2 or the fork lift truck 3 (Step
#105).
And the external management server H3 then calculates a single tag
determination distance which is the distance between the worker 2
or the fork lift truck 3 and the article transport vehicle 1 based
on the measured position of the worker 2 or the fork lift truck 3
(Step #106).
The external management server H3 determines if the single tag
determination distance is less than or equal to the remote distance
and greater than the neighboring distance, or is less than or equal
to the neighboring distance (see FIG. 5), and sets the first upper
limit speed as a deceleration command speed for the single tag
determination distance if it is less than or equal to the remote
distance and greater than the neighboring distance, and sets the
second upper limit speed as the deceleration command speed for the
single tag determination distance if it is less than or equal to
the neighboring distance, and stores it in a temporary memory (Step
#107).
The external management server H3 then commands the deceleration
command speed that is the lower speed between the deceleration
command speed that is calculated at Step #104, is stored in the
temporary memory, and corresponds to the multiple tag determination
distance, and the deceleration command speed that is calculated at
Step #107, is stored in the temporary memory, and corresponds to
the single tag determination distance (Step #108).
The external management server H3 determines whether there is any
object for which position measurement has not been completed in the
cycle among the interfering objects (that is, all the workers 2 and
fork lift trucks 3) that exist in the detection target area E (Step
#109), and performs the processes of steps #101-#108 until position
measurement is competed for all the interfering objects.
And the external management server H3 is configured to repeat the
operations in the flow chart in FIG. 10 from the beginning when
position measurement is completed for all the interfering
objects.
In the present embodiment, the travel of the article transport
vehicle is made safer by providing two ways to determine the
deceleration command based on the position of the interfering
object (the worker 2 or the fork lift truck 3) measured based on
the position of the wireless tags 22 as described above.
Second Embodiment
The second embodiment in accordance with the present invention is
described next with reference to FIGS. 11 and 12.
The second embodiment is different from the first embodiment only
in the processes that the external management server H3 performs
based on the position measurement process performed by the wireless
position measuring system 21. Accordingly, only the features that
are different from those in the first embodiment are described here
and descriptions for the features that are identical to those in
the first embodiment are omitted.
Specifically, the external management server H3 commands the tag
position measuring device 24 of the wireless position measuring
system 21 to calculate the positions of the two wireless tags 22
associated with, or carried by, the worker 2 or the fork lift truck
3 (step #201).
The external management server H3 next commands the wireless
position measuring system 21 to measure, as the multiple tag
position measurement process, the position of the midpoint of the
two wireless tags 22 as the position of the worker 2 or the fork
lift truck 3 (Step #202).
And the external management server H3 then calculates the multiple
tag determination distance which is the distance between the worker
2 or the fork lift truck 3 and the article transport vehicle 1
based on the measured position of the worker 2 or the fork lift
truck 3, and stores the multiple tag determination distance in the
temporary memory (Step #203).
The external management server H3 next commands the wireless
position measuring system 21 to measure, as the single tag position
measurement process, the position of one of the two wireless tags
22 as the position of the worker 2 or the fork lift truck 3 (Step
#204).
And the external management server H3 then calculates the single
tag determination distance which is the distance between the worker
2 or the fork lift truck 3 and the article transport vehicle 1
based on the measured position of the worker 2 or the fork lift
truck 3, and stores the single tag determination distance in the
temporary memory (Step #205).
The external management server H3 determines whether both of the
multiple tag determination distance which was calculated at Step
#203 and was stored in the temporary memory and the single tag
determination distance which was calculated at Step #205 and was
stored in the temporary memory are less than or equal to the low
speed distance (Step #206).
If it is determined, at Step #206, that both of the multiple tag
determination distance and the single tag determination distance
are less than or equal to the low speed distance (i.e., "Yes" at
Step #206), then the external management server H3 calculates the
deceleration command speed that corresponds to the shorter distance
between the multiple tag determination distance and the single tag
determination distance, and stores the deceleration command speed
in the temporary memory (Step #207).
If it is determined, at Step #206, that both of the multiple tag
determination distance and the single tag determination distance
are not less than or equal to the low speed distance (i.e., "No" at
Step #206), then the external management server H3 next determines
whether one of the multiple tag determination distance and the
single tag determination distance is less than or equal to the low
speed distance (Step #208).
If it is determined, at Step #208, that one of the multiple tag
determination distance and the single tag determination distance is
less than or equal to the low speed distance (i.e., "Yes" at Step
#208), then the external management server H3 calculates the
deceleration command speed that corresponds to the determination
distance that is less than or equal to the low speed distance, and
stores the deceleration command speed in the temporary memory (Step
#209).
Subsequent to the process at Step #207 or Step #209, the external
management server H3 issues a deceleration command specifying the
deceleration command speed which was calculated and stored in the
temporary memory (Step #210).
The external management server H3 determines whether there is any
object for which position measurement has not been completed in the
cycle among the interfering objects (that is, all the workers 2 and
fork lift trucks 3) that exist in the detection target area E (Step
#211), and performs the processes of steps #201-#210 until position
measurement is competed for all the interfering objects.
And the external management server H3 is configured to repeat the
operations in the flow chart in FIGS. 11 and 12 from the beginning
when position measurement is completed for all the interfering
objects.
In the present embodiment, the travel of the article transport
vehicle is made safer by providing two ways to determine the
distance between an interfering object (the worker 2 or the fork
lift truck 3) and the article transport vehicle 1 based on the
position of the interfering object measured based on the position
of the wireless tag 22 as described above.
Alternative Embodiments
(1) In the first or second embodiment described above, the facility
is configured to reduce the normal travel speed to a lower speed
based on the travel condition.
However, for example, same normal travel speed may be used for a
straight path portion and for a curved path portion in the travel
path, and same normal travel speed may be used for the high load
condition and the low load condition so that the facility may be
configured not to reduce the normal travel speed to a lower speed
even if the travel condition changes.
(2) In the first or second embodiment described above, the
auxiliary travel controller for controlling the operation of the
travel actuating device 7 based on the detected information from
the presence detector is incorporated within the presence detector.
However, the auxiliary travel controller may be provided
independently and separately from the presence detector. Further,
the vehicle side travel controller may perform the function of the
auxiliary travel controller.
(3) In the first or second embodiment described above, the small
area detector (position detector 19) is configured to issue the
deceleration command to the vehicle side travel controller of the
article transport vehicle 1 if and when the distance from the
article transport vehicle 1 to the interfering object becomes less
than or equal to the low speed distance, based on the detected
position information of an interfering object and the travel
position information of the article transport vehicle 1, and to
transmit the interfering object information to the presence
detector if and when the distance from the article transport
vehicle 1 to the interfering object becomes less than or equal to
the deceleration distance.
However, the small area detector (position detector 19) may be
configured to perform only one of the issuance of the deceleration
command to the vehicle side travel controller and the transmission
of the interfering object information to the presence detector.
The small area detector (position detector 19) receives the travel
position information for the article transport vehicle 1 by
wireless transmission from the travel position detector 13 in the
embodiments described above. However, the travel position
information for the article transport vehicle 1 may be obtained
through position detection of the article transport vehicle 1 by
the small area detector.
(4) In the first or second embodiment described above, the large
area detector and the small area detector are provided as the
position detectors 19.
However, only one of the large area detector and the small area
detector may be provided as the position detector 19.
In addition, the detection target area E for the large area
detector (position detector 19) is defined such as to include all
of the areas where the travel path L is installed.
However, the detection target area E may be defined to include only
a part of area where the travel path L is installed.
(5) In the first or second embodiment described above, the low
speed distance is defined to be the same distance for different
kinds of interfering objects.
However, for example, the facility may be configured such that the
deceleration command is not issued even if the distance from the
article transport vehicle 1 to the interfering object becomes less
than or equal to the remote distance or the long distance for an
interfering object that moves slowly and for an interfering object
that would have only a small impact even if it interferes, or
contacts, with the article transport vehicle 1 and such that the
deceleration command is not issued only if the distance from the
article transport vehicle 1 to the interfering object becomes less
than or equal to the intermediate distance or the neighboring
distance.
Thus, the facility may be configured so that the low speed distance
may be set to be different depending on the kind of the interfering
object.
(6) In the first or second embodiment described above, the low
speed distance for when an interfering object is located forwardly
of the article transport vehicle 1 in the travel direction is
defined to be different from the low speed distance for when an
interfering object is located rearwardly of the article transport
vehicle 1 in the travel direction.
However, these low speed distances may be defined to be the
same.
(7) In the first or second embodiment described above, the reduced
travel speed to which the target travel speed is changed when the
deceleration command is issued from the external managing device
and the reduced travel speed to which the target travel speed is
changed when the interfering object is detected by the presence
detector are defined to be the same speed (the first upper limit
speed or the second upper limit speed).
However, these reduced travel speeds may be defined to be
different.
In addition, although the first upper limit speed and the second
upper limit speed are defined as the reduced travel speed in the
above-described embodiments, three or more upper limit speeds
(e.g., a third upper limit speed) or only one upper limit speed
(e.g., first upper limit speed) may be defined as the upper limit
speed.
In addition, a stop speed for stopping the article transport
vehicle 1 may be defined as the reduced travel speed to which the
target travel speed is changed when a deceleration command is
issued from the external managing device.
Incidentally, the operation of the travel actuating device 7 may be
controlled to match the target travel speed for the article
transport vehicle 1 with the stop speed when the target travel
speed is changed to the stop speed.
Or, the operation of the electric-power interrupting device 18 may
be controlled to match the target travel speed of the article
transport vehicle 1 with the stop speed.
And in the embodiments described above, the first upper limit
speed, the second upper limit speed, and the stop speed are defined
as the reduced travel speed to which the target travel speed is
changed when an interfering object is detected by the presence
detector.
However, only one or two of these three speeds may be defined.
Or, four or more speeds may be defined, for example, by defining a
third upper limit speed.
(8) In the first or second embodiment described above, the
monitoring camera 20 is provided as the small area detector.
However, other detecting devices, such as a mat switch may be
provided as the small area detector.
While an Axi-Vision camera (a three-dimensional distance-mapping
imaging camera) is provided as the monitoring camera 20, other
cameras, such as, a stereoscopic camera, or an infrared camera may
be provided as the monitoring camera 20.
(9) In the first or second embodiment described above, an example
is described in which UWB wireless tags configured to transmit UWB
wireless signals as wireless signals for position measurement and
UWB receivers configured to communicate with these tags are
provided as the large area detector.
Instead, any of the various wireless communication systems such as,
wireless signals that are in compliance with such a
telecommunications standard as IEEE802.11n as wireless signals for
position measurement, wireless tags configured to transmit wireless
signals through wireless LAN, and a receiver configured to
communicate with these tags may be adapted.
In the embodiment described above, an example is described in which
the wireless tags are active tags.
However, as wireless tags, various kinds of wireless tags, such as
hybrid tags that are used in combination with passive RFID tags may
be adapted.
(10) In the first or second embodiment described above, the
position detector 19 is configured to transmit interfering object
presence information to the presence detector.
However, the position detector 19 may be configured to transmit the
information directly to the vehicle side travel controller without
communicating the information via the ground side travel
controller.
Note that, in this case, the vehicle side travel controller is
configured to change the target travel speed from the normal travel
speed to the reduced travel speed if and when interfering object
presence information is received from the position detector 19
while the target travel speed is set to a normal travel speed.
(11) In the first or second embodiment described above, one article
transport vehicle is provided in the article transport
facility.
However, two or more article transport vehicles may be provided in
the article transport facility.
In addition, while an example is described in which the article
transport vehicle is the kind that operates without a human
operator therein. However, the article transport vehicles only need
to be able to travel autonomously, and thus may be of a kind that
is configured to operate with a human operator in it.
In addition, apart from a pallet and goods and things supported by
the pallet, an article to be transported may be a carton case, a
container, or living things, such as an animal including human.
(12) In the first or second embodiment described above, the
detection target area E consists of a single area.
However, the detection target area E may consists of a plurality of
areas where the corresponding number of groups of base units 23 are
provided with each group provided to an area (four base units 23
for each area in the embodiments described above).
In addition, the shape of the detection target area E and the
installation locations of the base units 23 in the detection target
area E may be suitably changed.
For example, the detection target area E does not have to be
rectangular as in the embodiments described above but may be
circular instead.
Also, the installing locations of the base units 23 do not have to
be along the peripheral edge of the detection target area E as in
the embodiments described above.
Instead, the base units 23 may be installed within the detection
target area E.
And three or the five or more base units 23 may be provided to the
detection target area E.
Although a single detection area e is defined in the embodiments
described above, a plurality of small area detectors may be
provided and a plurality of detection areas e may be defined.
(13) In the first or second embodiment described above, a facility,
in which two wireless tags 22 are carried by each worker 2 and in
which two wireless tags 22 are carried by the fork lift truck 3, is
described.
However, three or more wireless tags 22 may be carried by each
worker 2 and in which three or more wireless tags 22 may be carried
by the fork lift truck 3.
In this case, in the multiple tag position measurement process
described above, the position that is obtained by averaging the
positions of the wireless tags 22 assigned to the worker 2 or the
fork lift truck 3 may be calculated and derived as the position of
the worker 2 or the fork lift truck 3.
And in the single tag position measurement process described above,
the position of one of the wireless tags 22 assigned to the worker
2 or the fork lift truck 3 may be calculated and derived as the
position of the worker 2 or the fork lift truck 3.
(14) In the first or second embodiment described above, a
configuration in which the position measurement process is
repeatedly performed at every predetermined cycle is described.
However, the cycle in which the position measurement process is
performed may be changed flexibly depending on the number of the
wireless tags 22 that exist in the detection target area E.
More specifically, if T [sec] is the amount of time required to
take a measurement on one wireless tag 22, and if n is the number
of the wireless tags 22 that exist in the detection target area E,
then the cycle may be set to be equal to T.times.n [sec].
(15) In the first and second embodiment described above, all four
base units 23 are assigned to one detection target area E.
However, for example, the detection target area E may be divided
into a plurality of areas.
And a group of two or more base units 23 may be assigned to each of
the plurality of areas.
In this case, the groups of base units 23 assigned to the
respective areas may perform polling of the wireless tags 22
simultaneously.
(16) In the embodiments described above, an example is described in
which the low speed areas are defined in advance as semi-circular
areas (area D1 and area D2 in FIG. 5) which share the same center
at the position of the article transport vehicle 1, which spread
forwardly of the article transport vehicle 1, and whose radii are
equal to the predetermined low speed distances.
However, the low speed areas are not limited to the areas described
above. For example, as shown in FIG. 13, the low speed areas
defined in advance in the external management server H3 may be
fan-shaped that spreads laterally toward the front from the front
of the article transport vehicle 1.
In FIG. 13, the low speed area (area D2) whose radius is equal to
the neighboring distance is defined as a fan-shaped area that spans
45 degrees to each side from an imaginary line extending straight
forward from the article transport vehicle 1 (i.e., with the
central angle of 90 degrees) and that has its center at a reference
position located near the center of the article transport vehicle
1.
And the low speed area (area D1) whose radius is equal to the
neighboring distance is defined as a fan-shaped area that spans 30
degrees to each side from the imaginary line extending straight
forward from the article transport vehicle 1 (i.e., with the total
angle of 60 degrees) and that has its center at the reference
position located near the center of the article transport vehicle
1.
In addition, the angle by which the fan-shaped area spread is not
limited to the values mentioned above but can be defined
suitably.
Also, while, in FIG. 13, the area D2 is defined to have a greater
angle by which the fan-shaped area spreads to each side from the
imaginary line extending straight forward from the article
transport vehicle 1 than the area D1, the area D1 may be defined to
have a greater angle by which the fan-shaped area spreads to each
side from the imaginary line extending straight forward from the
article transport vehicle 1 than the area D2.
In addition, the low speed areas in accordance with an alternative
embodiment may have its outer edge so shaped that the distance from
the article transport vehicle 1 to the outer edge is at its maximum
at the point on the outer edge that is located straight forward
from the article transport vehicle 1 and decreases outwardly in
either lateral direction.
That is, as shown in FIG. 14, the low speed areas may consist, for
example, of an area D1 which is of a half-elliptical shape or an
elongated circle which has its center at the article transport
vehicle 1 and with its major axis having the length of the remote
distance (25 m) and extending in the travel direction of the
article transport vehicle 1 and an area D2 which is of a
half-elliptical shape or an elongated circle having its center at
the article transport vehicle 1 and with its major axis having the
length of the neighboring distance (15 m) and extending in the
travel direction of the article transport vehicle 1.
In addition, in FIG. 14, the distance from the article transport
vehicle 1 to the outer edge of the area D1 is less than the
distance to the outer edge of the area D2 at positions near each
lateral side of the article transport vehicle 1.
However, the distance from the article transport vehicle 1 to the
outer edge of the area D1 may be greater than the distance to the
outer edge of the area D2 at positions near each lateral side of
the article transport vehicle 1.
That is, the areas may be so shaped that the greater the length of
major axis is, the greater the length of the minor axis is.
Further, the areas (area A1, area A2, and area A3) corresponding to
the deceleration distances set by the sensor controller 16 and the
camera control portion (not shown) may also be shaped such that the
distance from the article transport vehicle 1 to the outer edge is
at its maximum at the point on the outer edge that is located
straight forward from the article transport vehicle 1 and decreases
outwardly in either lateral direction from the straight forward
direction.
That is, for example, as shown in FIG. 14, the following three
areas may be defined: an area A1 which is of a half-elliptical
shape or an elongated circle having its center at the interfering
object sensor 15 with its major axis having its length equal to the
long distance (20 m) and extending along the travel direction of
the article transport vehicle 1, an area A2 which is of a
half-elliptical shape or an elongated circle having its center at
the interfering object sensor 15 with its major axis having its
length equal to the intermediate distance (8 m) and extending along
the travel direction of the article transport vehicle 1 and, an
area A3 which is of a half-elliptical shape or an elongated circle
having its center at the interfering object sensor 15 with its
major axis having its length equal to the short distance (2 m) and
extending along the travel direction of the article transport
vehicle 1.
In addition, the areas A1, A2, and A3 may be defined such that the
greater the length of the major axis is, the shorter the length of
the minor axis is, as with the areas D1, and D2.
In addition, in FIG. 14, each of the areas A1, A2, A3, D1, and D2
is of a half-elliptical shape or an elongated circle whose major
axis extends in the travel direction of the article transport
vehicle 1.
However, shapes other than the half-elliptical shape or elongated
circle described above may be adapted as long as the shapes are
such that the distance from the article transport vehicle 1 to the
outer edge is at its maximum at the point on the outer edge that is
located straight forward from the article transport vehicle 1 and
decreases outwardly in either lateral direction from the straight
forward direction.
In addition, it is possible to define the areas so as to have: a
mixture of semicircular areas and fan-shaped areas shown in FIG.
13; a mixture of semicircular areas and areas having a
half-elliptical shape or an elongated circle shown in FIG. 14; a
mixture of semicircular areas, fan-shaped areas shown in FIG. 13,
and areas having a half-elliptical shape or an elongated circle
shown in FIG. 14; or a mixture of fan-shaped areas shown in FIG. 13
and areas having a half-elliptical shape or an elongated circle
shown in FIG. 13.
* * * * *